This invention pertains to double-barrel, dual caliber, firearms.
The benefits of a dual caliber gun have been set forth in various periodicals. It has been found that such guns are useful when camping in areas where there are dangers from both large and small animals. A large caliber gun is needed in case of large animals such as bears. In the case of small creatures such as rats or snakes a small caliber gun is preferred. Dual caliber revolvers are even more important in survival situations, for example downed aircraft or lost hunters. In such circumstances it is important to have a revolver because it can be easily carried, and a dual caliber revolver can be used not only for defensive purposes, but for hunting both small and large animals. A small caliber gun is best for hunting small game such as rabbits and squirrels, whereas, a large caliber gun can be used for hunting larger animals such as deer. Using shotshell cartridges, the large caliber gun can also be used for hunting flying animals such as quail. Since the gun will fire two different sized cartridges, it is not rendered useless if only one size cartridge is available.
Dual caliber revolvers also come into consideration as training weapons. Since it is easier for beginners to master smaller caliber pistols with less recoil than the military 45 caliber automatics, it is not uncommon in handgun training to start troops firing smaller caliber pistols. As a result their training is more thorough and the transition to higher caliber handguns is easier and faster. The dual caliber gun of this invention would cost very little more to manufacture than the single gun, and hence would be a practical approach to the two gun training system.
Double barrel guns firing two sizes of cartridges are described in the prior art in such references as Guns & Ammo, June, 1975, p 42, and U.S. Pat. Nos. 943,819, 990,669 and 1,042,145. However each of these guns is subject to certain disadvantages. In the revolver shown in U.S. Pat. No. 943,819 the larger caliber chamber must be empty when the smaller caliber cartridge is fired. If all the chambers are loaded, the gun will fire both its large and small cartridges. Moreover, since the firing pins are not identical, uneven percussion of small and large caliber cartridges is quite likely, rendering the gun unreliable. On impact one cartridge can absorb most of the energy so that the other cartridge may not fire. There is also the disadvantage of having to unload to shoot small game. In that case, survival capability is sacrificed, defeating a purpose of the gun.
The design in U.S. Pat. No. 990,669 is subject not only to the complexities involved in two triggers, but also to a complex cocking mechanism. In order to change cartridge selections, the operator must cock the hammer only halfway, turning the cylinder one-twelfth of its revolution. However to determine whether to fully cock the hammer, or to half-cock it, he must ascertain which chamber is in use. It is not seen how this can be done without the user looking in the cylinder with the gun pointed toward him.
In U.S. Pat. No. 1,042,145 we see an unreliable tappet-hammer design. Because of the small distance between the point of impact and the point of rotation or fulcrum of the tappet, much of the impact energy is transferred to the fulcrum. Therefore, an extremely strong mainspring is required in order for the gun to function properly. This however renders trigger pull difficult, and accelerates wear of the mechanism which absorbs the heavy blow of the hammer.
All of these prior art pistols have one barrel below the other one. If the barrels are far apart as they are in the gun shown in Guns & Ammo, the gun possesses an inherent accuracy disadvantage. A slight rotation of the operator's hand will deliver the shot to the left or right of the point sighted over the upper barrel. In addition, as pointed out in the Guns & Ammo article the lockwork of the gun has been extensively changed. This is true of all of the prior art guns. They differ so drastically from standard guns that manufacture would be expensive and reliability questionable.
In accordance with this invention a more reliable dual caliber gun is provided which has a single trigger and normal spring action. Moreover the firing mechanism of the gun is unchanged from its normally manufactured single caliber counterpart.